Modified filler composition, method for making same, pulp and paper using same

ABSTRACT

A modified filler composition used in papermaking is provided. The modified filler composition contains nanofibrillated cellulose having a carboxyl content of about 0.05 to about 1.5 mmol/g, and filler having positive charge.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to People's Republic of China Patent Application No. 201310047279.4, filed Feb. 5, 2013, which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a modified filler composition used in the field of papermaking, a method for making the modified filler composition, and a pulp and a paper using the modified filler composition.

2. Description of Related Art

In the field of papermaking, adding filler to the paper pulp can effectively lower the cost. However, most filler particles can't bond the negatively charged fiber in the pulp effectively. Furthermore, the surface of the filler generally lacks carboxyl groups and hydroxyl groups, making it unable to form significant hydrogen bonds with the fiber in the pulp. Therefore, the filler and the fiber have relatively little affinity for each other, which can make the filler retention low. In addition, filler in the paper may inhibit the bonding of fiber to fiber, thereby reducing the strength of paper.

Therefore, there is room for improvement within the art.

DETAILED DESCRIPTION

The nanofibrillated cellulose (NFC) used in this disclosure is made by the traditional TEMPO catalytic oxidation method. The method includes the following steps: (1) providing plant fiber material, the plant fiber material being selected from softwood, hardwood, gramineae plant fiber, or any combination thereof; (2) oxidizing the plant fiber material using a TEMPO-NaBr—NaClO system or a TEMPO-NaClO—NaClO₂ system; and (3) mechanically treating the oxidized fiber by using at least one of a high-shear dispersion machine, an ultrasonic processor, a high-pressure homogenizer, or a microfluidic device.

The NFC made by the TEMPO catalytic oxidation method contains water soluble nano-fibrillated cellulose and derivatives thereof The NFC has carboxyl groups, and the carboxyl content can be adjusted by adjusting the dosage of the oxidant during the TEMPO catalytic oxidation process. The NFC have a dimension of about 100 nm to about 2000 nm in length, and about 4 nm to about 200 nm in diameter.

Micro-fibrillated cellulose (MFC) is a semi-finished product during the preparation process of the NFC. When fibrillation is substantially complete, NFC is obtained. When the fibrillation is only partially carried out, MFC is obtained. MFC has a relatively more complex composition, containing both water-soluble cellulose and water-insoluble cellulose. The water-soluble cellulose generally comprises nanocrystalline cellulose (NCC), NFC, and oligosaccharides, for example. Note: the NCC and the NFC has differences in degree of crystallinity and length to diameter ratio. The NCC has a high degree of crystallinity of more than 70%, sometimes the degree of crystallinity of the NCC can reach 85% to 97%. While the NFC has a degree of crystallinity of less than 70%. The degree of crystallinity of the NFC is generally in a range from 20% to 70%. The NCC has a length to diameter ratio generally less than 250. The NFC has a length to diameter ratio more than 250, generally more than 500. Sometimes, the length to diameter ratio of the NFC can reach 2000.

A pulp-making process includes the following steps:

Step 1: preparing a modified filler composition.

Filler and water are mixed together to make a filler slurry having a concentration of about 10% to about 50%, then the NFC is added to the filler slurry, and stirred for about 5 to 15 minutes, wherein the dry weight of the NFC is about 0.1% to about 20% of that of the filler. In this embodiment, the dry weight of the NFC is about 0.1% to about 10% of that of the filler. The content of carboxyl groups of the NFC is in the range from about 0.05 to about 1 5 mmol/g, or more specifically in the range from about 0.1 to about 1.0 mmol/g.

The filler particles are positively charged. The filler can be any known filler material used in paper manufacturing and, for example, may be selected from precipitated calcium carbonate (PCC), ground calcium carbonate (GCC), kaolin, alumina, and talc, or any combination thereof

The NFC has strong negative charge, while the filler particles have positive charge. Therefore, the negatively charged NFC are expected to bond on the surface of the positively charged filler particles, causing the modified filler composition to become negatively charged.

Step 2: adding the modified filler composition and a cationic polyelectrolyte into a pulp.

In this step, the modified filler composition may have a dry weight of 5% to 100% of that of the pulp, and the cationic polyelectrolyte may have a dry weight of 0.01% to 1% of that of the pulp. The cationic polyelectrolyte can be any cationic polyelectrolyte commonly used in the field of papermaking, such as cationic starch or cationic polyacrylamide. The cationic starch may be made by traditional method using starch and cationic etherifying agent.

As the cationic polyelectrolyte has strong positive charge, it is equivalent to a binder or a medium for coupling a strong negatively charged modified filler composition and the weak negatively charged pulp fiber together. Thus, filler retention can be improved through this enhanced interaction.

The modified filler composition in this disclosure contains NFC and filler, wherein the dry weight of the NFC may be from about 0.1% to about 20% of that of the filler. In this embodiment, the dry weight of the NFC may be about 0.1% to about 10% of that of the filler. The content of carboxyl groups in the NFC is in the range from about 0.05 to about 1.5 mmol/g, and more specifically in the range from about 0.1 to about 1.0 mmol/g.

The content of carboxyl groups in the NFC can be measured by the following steps: (1) NFC having a dry weight of 0.3 g, deionized water having a volume of 55 ml, and sodium chloride solution having a concentration of 0.01 mol/L and a volume of 5 ml are mixed together and stirred to make a mixture; (2) hydrochloric acid solution having a concentration of 0.1 mol/L is added to the mixture to adjust the pH value of the mixture to be about 2.5 to about 3.0; (3) then sodium hydroxide solution having a concentration of 0.04 mol/L is added to the mixture at a speed of 0.1 mL/min, and meantime the electrical conductivity of mixture is measured by an conductivity meter until the pH value of the mixture reach 11.0; (4) addition amount of the sodium hydroxide relative to the electrical conductivity of the mixture is plotted to obtain a curve figure; (5) consumption of the sodium hydroxide that reacts with the NFC can be calculated from the curve figure, and the content of carboxyl groups in the NFC can be calculated. Note: the electrical conductivity in the curve figure has falling stage, stationary stage and rising stage, the consumption of the sodium hydroxide solution during the stationary stage of the electrical conductivity in the curve figure represents the consumption of the sodium hydroxide that reacts with the NFC. Take the average from three times parallel experiments.

The filler particles are positively charged, and it can be measured by a particle charge detector (PCD) using filler slurry having a concentration of 10% to 20% at an ambient temperature. The model of the particle charge detector used in this disclosure is BTG PCD-04. The filler may, for example, be selected from precipitated calcium carbonate (PCC), ground calcium carbonate (GCC), kaolin, and talc.

The pulp made by the above-described pulp-making process contains the modified filler composition and the cationic polyelectrolyte, wherein the modified filler composition has a dry weight of 5% to 100% of that of the pulp, and the cationic polyelectrolyte has a dry weight of 0.01% to 1% of that of fiber in the pulp. The cationic polyelectrolyte can be any cationic polyelectrolyte commonly used in the field of papermaking, such as cationic starch or cationic polyacrylamide.

A paper is made using the above paper pulp by a traditional method which includes making a wet paper by getting water out of the paper pulp and drying the wet paper. The paper has a high filler retention; and in some embodiments the highest filler retention may reach more than 85%.

The NFC made by TEMPO catalytic oxidation method has a high specific surface area, high strength, high surface negative charge density and film-forming characteristics. In this disclosure, the NFC was used to modify the filler and provide the surface of the filler particles with carboxyl groups and negative charge. Then the modified filler composition together with the cationic polyelectrolyte was added into the paper pulp. The cationic polyelectrolyte can act as a binder or a medium for coupling the modified filler composition and the pulp fibers together. As a result, bonding between the modified filler composition and the pulp fiber is improved, and the filler retention can be effectively improved.

EXAMPLE 1

In this embodiment, the modified filler composition was prepared by using NFC having a carboxyl content of about 1.5 mmol/g and PCC, and the NFC had a dry weight of about 0.1% of that of the PCC. Then the modified PCC composition and a cationic starch was added to a Leaf bleached kraft pulp (LBKP) comprising hardwood fibers, wherein the modified PCC composition had a dry weight of about 25% of that of the LBKP, and the cationic starch had a dry weight of about 0.8% of that of the LBKP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the LBKP by directly adding a cationic starch slurry having a concentration of about 1% to the LBKP. Note: All the pulps used in Example 1 and the following Examples 2-12 and comparative Example 1 were produced by Asia Pulp &Paper Co., Ltd.

A wet paper was made by getting water out of the above LBKP added with the modified PCC composition and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 6.12%, and a filler retention of 26.07%.

COMPARATIVE EXAMPLE 1

In this comparative embodiment, the filler was unmodified PCC. The unmodified PCC and a cationic starch was added to a LBKP, wherein the PCC had a dry weight of about 25% of that of the LBKP comprising hardwood fibers, and the cationic starch had a dry weight of about 0.8% of that of the LBKP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the LBKP by directly adding a cationic starch slurry having a concentration of about 1% to the LBKP.

A wet paper was made by getting water out of the above LBKP added with the unmodified PCC and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 5.67%, and a filler retention of 24.04%.

EXAMPLE 2

In this embodiment, the modified filler composition was prepared by using NFC having a carboxyl content of about 1.5 mmol/g and PCC, and the NFC had a dry weight of about 1% of that of the PCC. Then the modified PCC composition and a cationic starch was added to a LBKP, wherein the modified PCC had a dry weight of about 25% of that of the LBKP, and the cationic starch had a dry weight of about 0.8% of that of the LBKP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the LBKP by directly adding a cationic starch slurry having a concentration of about 1% to the LBKP.

A wet paper was made by getting water out of the above LBKP added with the modified PCC composition and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 8.01%, and a filler retention of 34.83%.

EXAMPLE 3

In this embodiment, the modified filler composition was prepared by using NFC having a carboxyl content of about 1.5 mmol/g and PCC, and the NFC had a dry weight of about 5% of that of the PCC. Then the modified PCC composition and a cationic starch was added to a LBKP, wherein the modified PCC had a dry weight of about 25% of that of the LBKP, and the cationic starch had a dry weight of about 0.8% of that of the LBKP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the LBKP by directly adding a cationic starch slurry having a concentration of about 1% to the LBKP.

A wet paper was made by getting water out of the above LBKP added with the modified PCC composition and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 12.30%, and a filler retention of 56.1%.

EXAMPLE 4

In this embodiment, the modified filler composition was prepared by using NFC having a carboxyl content of about 1.5 mmol/g and PCC, and the NFC had a dry weight of about 10% of that of the PCC. Then the modified PCC composition and a cationic starch was added to a LBKP, wherein the modified PCC had a dry weight of about 25% of that of the LBKP, and the cationic starch had a dry weight of about 0.8% of that of the LBKP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the LBKP by directly adding a cationic starch slurry having a concentration of about 1% to the LBKP.

A wet paper was made by getting water out of the above LBKP added with modified PCC composition and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 13.36%, and a filler retention of 61.68%.

EXAMPLE 5

In this embodiment, the modified filler composition was prepared by using NFC having a carboxyl content of about 1.5 mmol/g and PCC, and the NFC had a dry weight of about 20% of that of the PCC. Then the modified PCC composition and a cationic starch was added to a LBKP, wherein the modified PCC had a dry weight of about 25% of that of the LBKP, and the cationic starch had a dry weight of about 0.8% of that of the LBKP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the LBKP by directly adding a cationic starch slurry having a concentration of about 1% to the LBKP.

A wet paper was made by getting water out of the above LBKP added with the modified PCC composition and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 14.36%, and a filler retention of 67.07%.

EXAMPLE 6

In this embodiment, the modified filler composition was prepared by using NFC having a carboxyl content of about 0.8 mmol/g and PCC, and the NFC had a dry weight of about 5% of that of the PCC. Then the modified PCC composition and a cationic starch was added to a LBKP, wherein the modified PCC had a dry weight of about 5% of that of the LBKP, and the cationic starch had a dry weight of about 0.8% of that of the LBKP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the LBKP by directly adding a cationic starch slurry having a concentration of about 1% to the LBKP.

A paper was made by using the above LBKP added with the modified PCC composition and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 1.16%, and a filler retention of 23.47%.

EXAMPLE 7

In this embodiment, the modified filler composition was prepared by using NFC having a carboxyl content of about 0.8 mmol/g and PCC, and the NFC had a dry weight of about 5% of that of the PCC. Then the modified PCC composition and a cationic starch was added to a LBKP, wherein the modified PCC had a dry weight of about 25% of that of the LBKP, and the cationic starch had a dry weight of about 0.8% of that of the LBKP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the LBKP by directly adding a cationic starch slurry having a concentration of about 1% to the LBKP.

A wet paper was made by getting water out of the above LBKP added with the modified PCC composition and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 11.52%, and a filler retention of 52.08%.

EXAMPLE 8

In this embodiment, the modified filler composition was prepared by using NFC having a carboxyl content of about 0.8 mmol/g and PCC, and the NFC had a dry weight of about 5% of that of the PCC. Then the modified PCC composition and a cationic starch was added to a LBKP, wherein the modified PCC had a dry weight of about 75% of that of the LBKP, and the cationic starch had a dry weight of about 0.8% of that of the LBKP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the LBKP by directly adding a cationic starch slurry having a concentration of about 1% to the LBKP.

A wet paper was made by getting water out of the above LBKP added with the modified PCC composition and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 24.53%, and a filler retention of 43.34%.

EXAMPLE 9

In this embodiment, the modified filler composition was prepared by using NFC having a carboxyl content of about 0.8 mmol/g and PCC, and the NFC had a dry weight of about 5% of that of the PCC. Then the modified PCC composition and a cationic starch was added to a LBKP, wherein the modified PCC had a dry weight of about 100% of that of the LBKP, and the cationic starch had a dry weight of about 0.8% of that of the LBKP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the LBKP by directly adding a cationic starch slurry having a concentration of about 1% to the LBKP.

A wet paper was made by getting water out of the above LBKP added with the modified PCC composition and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 28.16%, and a filler retention of 39.20%.

EXAMPLE 10

In this embodiment, the modified filler composition was prepared by using NFC having a carboxyl content of about 0.05 mmol/g and PCC, and the NFC had a dry weight of about 5% of that of the PCC. Then the modified PCC composition and a cationic starch was added to a LBKP, wherein the modified PCC had a dry weight of about 25% of that of the LBKP, and the cationic starch had a dry weight of about 0.8% of that of the LBKP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the LBKP by directly adding a cationic starch slurry having a concentration of about 1% to the LBKP.

A wet paper was made by getting water out of the above LBKP added with the modified PCC composition and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 7.16%, and a filler retention of 30.85%.

EXAMPLE 11

In this embodiment, the modified filler composition was prepared by using NFC having a carboxyl content of about 0.8 mmol/g and PCC, and the NFC had a dry weight of about 5% of that of the PCC. Then the modified PCC composition and a cationic starch was added to a NBKP, wherein the modified PCC had a dry weight of about 25% of that of the NBKP, and the cationic starch had a dry weight of about 0.8% of that of the NBKP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the NBKP by directly adding a cationic starch slurry having a concentration of about 1% to the NBKP.

A wet paper was made by getting water out of the above NBKP added with the modified PCC composition and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 7.76%, and a filler retention of 33.65%.

EXAMPLE 12

In this embodiment, the modified filler composition was prepared by using NFC having a carboxyl content of about 0.8 mmol/g and PCC, and the NFC had a dry weight of about 5% of that of the PCC. Then the modified PCC composition and a cationic starch was added to a APMP, wherein the modified PCC had a dry weight of about 25% of that of the APMP, and the cationic starch had a dry weight of about 0.8% of that of the APMP. The cationic starch was a quaternary ammonium salt type cationic cassava starch having a degree of substitution of 0.01 to 0.3, and the cationic starch was added to the APMP by directly adding a cationic starch slurry having a concentration of about 1% to the APMP.

A wet paper was made by getting water out of the above APMP added with the modified PCC composition and the cationic starch, and the wet paper was dried to be a paper. The paper had a basis weight of 70 g/m², an ash content of 12.70%, and a filler retention of 58.19%.

It is believed that the exemplary embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its advantages, the examples hereinbefore described merely being exemplary embodiments of the disclosure. 

1. A modified filler composition, comprising: filler having positive charge; and nanofibrillated cellulose, the nanofibrillated cellulose having a dry weight of about 0.1% to about 20% of that of the filler, the nanofibrillated cellulose having a carboxyl content of about 0.05 to about 1.5 mmol/g.
 2. The modified filler composition as claimed in claim 1, wherein the nanofibrillated cellulose has a dry weight of about 0.1% to about 10% of that of the filler.
 3. The modified filler composition as claimed in claim 1, wherein nanofibrillated cellulose has a carboxyl content of about 0.1 to about 1.0 mmol/g.
 4. The modified filler composition as claimed in claim 1, wherein the filler is selected from precipitated calcium carbonate, ground calcium carbonate, kaolin, and talc.
 5. The modified filler composition as claimed in claim 1, wherein the modified filler composition further comprises water.
 6. A method for making a modified filler composition, comprising: providing nanofibrillated cellulose having a carboxyl content of about 0.05 to about 1.5 mmol/g; mixing filler and water together to make a filler slurry, the filler having positive charge; adding the nanofibrillated cellulose to the filler slurry and stirring, the dry weight of the nanofibrillated cellulose being about 0.1% to about 20% of that of the filler.
 7. The method for making a modified filler composition as claimed in claim 6, wherein the nanofibrillated cellulose has a carboxyl content of about 0.1 to about 1.0 mmol/g.
 8. The method for making a modified filler composition as claimed in claim 6, wherein the dry weight of the nanofibrillated cellulose is about 0.1% to about 10% of that of the filler.
 9. The method for making a modified filler composition as claimed in claim 6, wherein the filler is selected from precipitated calcium carbonate, ground calcium carbonate, kaolin, and talc.
 10. The method for making a modified filler composition as claimed in claim 6, wherein the filler slurry has a concentration of about 10% to about 50%.
 11. A paper pulp, comprising: pulp fiber; modified filler composition having a dry weight of 5% to 100% of that of the pulp fiber; and cationic polyelectrolyte, the cationic polyelectrolyte having a dry weight of 0.01% to 1% of that of the pulp fiber, wherein the modified filler composition comprises nanofibrillated cellulose having a carboxyl content of about 0.05 to about 1.5 mmol/g; and filler having positive charge, and the dry weight of the nanofibrillated cellulose is about 0.1% to about 20% of that of the filler.
 12. The paper pulp as claimed in claim 11, wherein the dry weight of the nanofibrillated cellulose is about 0.1% to about 10% of that of the filler.
 13. The paper pulp as claimed in claim 11, wherein the nanofibrillated cellulose has a carboxyl content of about 0.1 to about 1.0 mmol/g.
 14. The paper pulp as claimed in claim 11, wherein the filler is selected from precipitated calcium carbonate, ground calcium carbonate, kaolin, and talc.
 15. The paper pulp as claimed in claim 11, wherein the cationic polyelectrolyte is cationic starch or cationic polyacrylamide.
 16. A paper, comprising: paper fiber; modified filler composition; and cationic polyelectrolyte, wherein the modified filler composition comprises nanofibrillated cellulose having a carboxyl content of about 0.05 to about 1.5 mmol/g; and filler having positive charge, and the dry weight of the nanofibrillated cellulose is about 0.1% to about 20% of that of the filler.
 17. The paper as claimed in claim 16, wherein the dry weight of the nanofibrillated cellulose is about 0.1% to about 10% of that of the filler.
 18. The paper as claimed in claim 16, wherein the nanofibrillated cellulose has a carboxyl content of about 0.1 to about 1.0 mmol/g.
 19. The paper as claimed in claim 16, wherein the cationic polyelectrolyte is cationic starch or cationic polyacrylamide. 